This invention concerns mechanical devices for transfering mechanical power between components with reciprocating motion and components with rotary motion.
U.S. Pat. application No. 706,291, filed July 19, 1976 and commonly owned with the present invention, discloses several embodiments of a variable speed transmission having a first element defining a pair of rolling surfaces of revolution about a first axis, a second element having a pair of rolling surfaces about a second axis intersecting the first at a point of axes intersection, a frame in which the first and second elements are supported to fix the angular orientation of the two axes, and a mechanical system for urging the respective rolling surfaces into frictional engagement with each other at two points of contact on opposite sides of the point of axes intersection. The rolling surfaces on one of the members are cone-like in shape whereas the rolling surfaces on the other element are ring-like and movable axially in opposite directions with respect to the point of axes intersection. The relative ratio of rolling surface radii at the points of contact may be made to vary to provide an infinitely variable speed ratio.
In one embodiment, the first element is provided with the cone-like rolling surfaces and is rotatable about the first axis at a velocity .omega.. The second element carries the ring-like rolling surfaces and is journalled in a crank-like support such that the second axis may travel in a biconical path about the first axis at a velocity .alpha.. The second element may or may not undergo rotation about the second axis at a velocity .beta.. Also, the disclosure incorporates a mechanical linking system by which any two of the components rotating at velocities .alpha., .beta. and .omega. may be interconnected or in which all three of such velocity components may be connected by means of an epicycloidal train.
In the operation of one embodiment, the first element on which the cone-like rolling surfaces are provided is connected directly with an output shaft and thus rotatable at a velocity .omega.. The second element is driven in nutational movement in which the second axis travels in a biconical path about the first axis at a velocity .alpha.. The second element is prevented from rotating on the second axis (.beta.=0) by a mechanical linkage in the form of conical gears having an apex coincident with the point of axes intersection, one of which gears is fixed to the frame while the other is carried by the second element. Thus, the output shaft velocity .omega. will be related to input velocity .alpha. as a result of the ratio of radii at the two points of rolling friction contact between the rolling surfaces on the first and second elements.
In an alternative embodiment, the second element is driven at one end and connected also at one end by a linkage which prevents rotation of the second element on the second axis without impeding nutational movement of the second element. The preferred linkage is in the form of an annular diaphragm provided with concentric corrugations capable of flexing in a radial direction while being resistant to flexure in a circumferential direction. In addition, the two couples of rolling surfaces are generated by curves with radii comparable in magnitude and long compared with the average distance of each surface from its axis of revolution. Such radii are, for example, approximately twenty times the average distance. As a result of this latter feature, the distance of relative axial movement between the rolling surfaces to achieve speed ratio variation is shortened and overall efficiency is increased.